> . . . cabs are vastly better than most offerings from Uber, since the car is designed for transporting paying passengers . . .
> Aren't the levels of Uber that allow a Prius to be used much, much cheaper than a black cab?
If you want a larger car, you can get it. You'll just pay a bit more.
> On paper, sure. In practice, I find that Uber is nearly constantly in surge pricing in London. I've had it several times now where I Was riding in a group, same start point same destination - some people in ubers, some in black cabs. Again, with normal pricing Uber should be cheaper, but since it's very often at 1.5x-2x multiplier, it works out the same or actually more expensive than a black cab. And sure, there is the higher tier of ubers too, but it's usually showing me 20-30 minute wait for a cab for a nicer car.
Seems like the fact that there is constantly surge pricing and long waiting time means that there are too few Uber drivers, even in "low quality" cars, to meet demand. Your complaints sound like the old joke about prison food: it tastes terrible and the portions are too small.